Operation Niagara was one of intelligence operations conducted by US Military during Vietnam War. This operation mainly conducted in Khe Sanh, an area located near the border of North Vietnam and South Vietnam. During this operation, US Military airdropped thousands of the new Unattended Ground Sensors (UGS) around the base to monitor North Vietnamese activity, and intelligence analysts at highly secret sigint bases in far-off Thailand were soon receiving conversations between puzzled NVA soldiers along the lines.
Operation Niagara around Khe Sanh was a huge intelli-gence success, and by mid-January 1968 it had identified 15,000 men of the NVA 325th and 304th Divisions definitely closing in on the US base. Patrols from the US Marines began to clash with NVA regulars digging in on the surrounding hills as the communist noose tightened.